Rotary piston machine with internal splined shaft

ABSTRACT

The invention relates to a gerotor type rotary piston machine. The casing has a main axis and the gerotor gear set includes an externally toothed star member which is rotatable about its own axis and orbital about the casing main axis. A main drive shaft is rotatable about the casing axis and a universal type wobble shaft connects the main shaft to the gerotor star member. An annularly shaped valve is mounted in said casing for rotation about the casing main axis. The valve is in surrounding relation to the wobble shaft and is axially positioned between the two ends of the wobble shaft. The wobble shaft has a cross bore and a diametrically extending drive member attached to the valve extending through the cross bore. The wobble shaft has a longitudinally extending bore and a keying shaft having a stem in this bore engages the valve drive member in driving relation thereto. The keying member is needed because the wobble shaft has a compound rotating and orbiting motion whereas the valve only has a rotating motion and something more than a simple shaft and bore connection between them is required.

iJite Ohrberg States Patent [191 1 ROTARY PISTON MACHINE WITH INTERNAL SPLINED SHAFT [75] Inventor: Carl Verner Ohrberg, Nordborg,

Denmark [73] Assignee: Dantoss A/S, Nordborg, Denmark [22] Filed: May 31, 1973 [21] App]. No.: 365,435

[30] Foreign Application Priority Data Primary Examiner-C. J. l-lusar Assistant ExaminerLeonard Smith 57 1 ABSTRACT The invention relates to a gerotor type rotary piston machine. The casing has a main axis and the gerotor gear set includes an externally toothed star member which is rotatable about its own axis and orbital about the casing main axis. A main drive shaft is rotatable about the casing axis and a universal type wobble shaft connects the main shaft to the gerotor star member. An annularly shaped valve is mounted in said casing for rotation about the casing main axis. The valve is in surrounding relation to the wobble shaft and is axially positioned between the two ends of the wobble shaft. The wobble shaft has a cross bore and a diametrically extending drive member attached to the valve extending through the cross bore. The wobble shaft has a longitudinally extending bore and a keying shaft hav ing a stem in this bore engages the valve drive member in driving relation thereto. The keying member is needed because the wobble shaft has a compound rotating and orbiting motion whereas the valve only has a rotating motion and something more than a simple shaft and bore connection between, them is required.

6 Claims, 4 Drawing Figures ROTARY PISTON MACHINE WITH INTERNAL SPLINED SHAFT The invention relates to a rotary-piston machine with internal splined shaft and with a rotatable externally toothed wheel and an internally toothed ring secured to the housing which mesh with each other, in which machine the toothed wheel is rotatably connected to the main shaft through a first universal-joint shaft and to a rotary slide through a second universal-joint shaft, and the two universal-joint shafts each mesh by means of a coupling head with a toothed coupling portion or equivalent means on the toothed wheel.

Rotary-piston machines of this kind; can be used aspu pumps or as motors. Since the filling and emptying cycle of the chambers formed between the toothed wheel and the toothed ring takes place at a greater speed than that at which the main shaft rotates, the machine can constitute a pump capable of delivering large volumes or a high-torque motor. The rotary slide together with an opposed surface on the housing constitutes a distributor valve which ensures that the chambers are filled and emptied in the correct sequence and at the correct speed, although the slide rotates only at the same speed as the main shaft. For this purpose, the number of openings in the rotary slide is equal to twice the number of teeth on the toothed wheel, and the number of openings in the opposite surface on the housing is equal to the number of teeth on the toothed ring.

In a known construction (German Pat. application No. 1,931,143 as laid open) the toothed wheel and the toothed ring are disposed between the point at which the main shaft projects from the housing and the rotary slide. The two universal-joint shafts are disposed one behind the other in the longitudinal direction. Since the length of at least the first universal-joint shaft may not be less than a predetermined minimum, as otherwise the angle of inclination in relation to the axis of the main shaft becomes too great, this results in a construction of relatively great length. The length of the construction is further increased as a result of the connecting ports being located at that side of "the rotary slide remote from the toothed wheel.

Machines are also known in which the rotary slide is fitted between the toothed wheel and toothed ring on the one hand and the point at which the main shaft projects from the housing on the other (German Patent Specification 1,553,004 as accepted). However, in these machines, the rotary slide is securely connected to the main shaft, and only a single universal-joint shaft is provided between the toothed ring and the main shaft or the rotary slide. On account of the play in the coupling at the two ends of the universal-joint shaft and because of the torsion occurring in the universal-joint shaft under high torque, there arises the possibility of the rotary slide no longer being accurately aligned with the toothed wheel under certain operating conditions, sothat a reduction in power results.

The object of the invention is to provide a rotarypiston machine with internal splined shaft of the initially-described kind in which the rotary slide remains aligned with the toothed ring irrespective of the machine load, said machine being of shorter length.

According to the invention, this object is achieved by housing, and by'the stem of the second universal-joint shaft extending into the interior of the first universaljoint shaft and being coupled to the rotary slide with the aid of a driving member which extends through substantially radial openings in the first universal-joint shaft, there being clearance between said member and the walls of said openings.

The length of the construction is reduced in that both the second universal-joint shaft and the rotary slide are fitted within the length occupied by the first universaljoint shaft. The connecting ports can also belocated in this zone. Since the rotary slide is still driven by the second universal-joint shaft, its position in relation to the toothed wheel is independent of the torque applied to the main shaft. The clearance in the radial openings permits both peripheral displacement between the first universal-joint shaft and the rotary slide and the usual angular movement of the first universal-joint shaft. The construction also takes into account the torques that are to be transmitted. A low torque suffices for driving the rotary slide, and this torque can be readily transmitted through the slimmer stem of the second universaljoint shaft. A bore in the interior of the universal-joint shaft causes no trouble as regards transmission of the v considerably higher main shaft torque, since the core of this shaft in any case makes little contribution towards the transmission of torque.

Particularly advantageous is a disc-shaped rotary slide which has axial grooves for engagement of the driving member. The use of a disc-shaped rotary slide results in a reduction of the length of the construction as compared with the constructionresulting from the use of a cylindrical rotary slide. Furthermore, the con- V necting ports can be readily fitted. In particular the disc-shaped rotary slide can be readily pushed on to the driving member with the aid of the axial grooves, so that a simple assembly is achieved.

That end of the second universal-joint shaft remote from the coupling head is expediently formed as a bifurcation which embraces the driving member, and an abutment surface for the coupling head is provided on the housing. With an arrangement of this kind, the second universal-joint shaft can be inserted into the first universal-joint shaft after the driving member has been fitted. It is then held in position by the abutment surface.

Particular advantage accrues if the driving member is a rod having a rectangular cross-section. A rod of this kind has two pairs of driving faces which act in theperipheral direction and for which the loads that occur 7 can be accurately calculated. Rods of other cross- The invention will now be described ingreater detail by reference to a preferred embodiment illustrated in the drawing, in which:

FIG. 1 shows a longitudinal section through a machine in accordance with the invention,

FIG. 2 is as'ection on the line A-A of FIG. 1, FIG. 3 shows another form of the arrangement illustrated in FIG. 2, and

FIG. 4 shows a third form of the arrangement illustrated in FIG. 2.

Proceeding from left to right, the machine housing consists of the following parts: an end-plate l, a main body part 2, a duct plate 3, a toothed ring 4 and a second end-plate 5, these parts being interconnected by screw-bolts 6, 7 and 8, and the interfaces being sealed off by means of O-rings 9, 10, 11 and 12.

A main shaft 13 is mounted in the main body part 2 with the aid of roller bearings 14 and in the duct plate 3 with the aid of a sliding bearing 15. The end-plate 1 has a seal 16 at the point where the main shaft 3 projects from the housing. The main shaft 13 has a bore 17 which terminates in a toothed coupling portion 18. A coupling head 19 of a first universal-joint shaft 20 meshes with this toothed portion. The second coupling head 21 of this shaft meshes with a toothed coupling portion 22 of a toothed wheel 23 which meshes with the teeth of the toothed ring 4, which teeth take the form of cylindrical rollers 24.

The stem of a second universal-joint shaft 26 extends through a bore of the first universal-joint shaft 20. A coupling head 27 of the second universal-joint shaft 26 is in engagement with the toothed portion 22 of the toothed ring 23. The other end of the shaft 26 is formed as a bifurcation 28. The bifurcation embraces a driving member 29 which takes the form of a rod having a rectangular cross-section and which extends through openings 30 in the first universal-joint shaft 20 and openings 31 in the main shaft 13, there being clearance between said driving member and the walls of said openings. The ends of the driving member 29 are disposed in axial grooves 32 in a rotary slide 33 which is mounted on the peripheral surface of the main shaft 13.

Provided in the main body part 2 of the housing are two connecting ports 34 and 35 which are used selectively for supplying and discharging a compressed fluid. Each port communicates with an annular groove 36 and 37 respectively, and these grooves are each aligned with the inlet openings of valve ducts 38 and 39 respectively which alternate with each other around the periphery of the rotary slide. To provide a clearer illustration, the valve duct 39 is displaced in the plane of the drawing. The outlets of these valve ducts cooperate with the inlets of connecting ducts 40 in the duct plate 3, which latter ducts each terminate between the bases of two adjacent teeth of the ring 4. If the machine is operated as a motor, and compressed fluid is supplied through the port 35, the toothed wheel 23 begins to rotate and drives the main shaft 13 through the first universal-joint shaft 20, and the rotary slide 33 through the second universal-joint shaft 26. As a result of the angular displacement of the valve ducts 38 and 39 relative to the connecting ducts 40, the chambers formed between the teeth of the wheel 23 and those of the ring 4 are alternately filled with compressed fluid and emptied again. Emptying is by way of the valve ducts 39 and the connecting port 34. If compressed fluid is supplied through the port 34 the motor turns in the opposite direction.

The driving member 29 is disposed approximately mid-way in the disc-shaped rotary slide 33, and its longitudinal axis is parallel with the plane of the disc. The two universal-joint shafts 20 and 26 execute a rotary movement and at the same time a tilting movement.

cylindrical driving members 29' and a complementarilv shaped opening 30. FIG. 4 illustrates a single cylindrical driving member 29" with a complementarily shaped opening 30".

During assembly, the rotary slide 33 can be easily pushed over the driving member 29 in the previously mounted main shaft 13 and associated first universaljoint shaft 20, prior to screwing on the duct plate 3. After the toothed wheel 23 has been fitted, the second universal-joint shaft 26 is pushed into the interior of the first universal-joint shaft and is held in position by an abutment surface 41 on the end-plate 5.

I claim:

1. A gerotor type rotary piston machine comprising a casing having a main axis, a gerotor gear set having an externally toothed wheel which is rotatable about its own axis and orbitable about said main axis, said wheel being internally splined, an internally splined main shaft rotatable about said axis, a wobble shaft having externally splined front and rear heads at opposite ends thereof in respective splined engagement with 7 said wheel and said main shaft, anannularly shaped valve mounted in said casing for rotation about said main axis, said valve being in surrounding relation to said main shaft and said wobble shaft between the opposite ends thereof, said main shaft and said wobble shaft having aligned and transversely extending cross bores, a diametrically extending drive member attached to said valve and extending through said main and wobble shaft bores, said wobble shaft having a longitudinal bore extending from said cross bore thereof to and through said from head of said wobble shaft, and drive connection means including a keying shaft having a stem mounted in said wobble longitudinal bore which engages said drive member.

2. A rotary piston machine according to claim I wherein the end of said stem is bifurcated and straddles said drive member, said keying shaft having a head portion at the end thereof opposite from said drive membet, and a casing portion having abutting engagement with said keying shaft head portion.

3. A rotary piston machine according to claim 1 wherein said drive member has a rectangular crosssection.

4. A rotary piston machine according to claim 1 wherein said drive member has a circular cross section.

5. A rotary piston machine according to claim 1 wherein said drive member has two parallelshaft portions. I

6. A rotary piston machine according to claim 5 wherein said parallel shaft portions have circularlcrosssections. 

1. A gerotor type rotary piston machine comprising a casing having a main axis, a gerotor gear set having an externally toothed wheel which is rotatable about its own axis and orbitable about said main axis, said wheel being internally splined, an internally splined main shaft rotatable about said axis, a wobble shaft having externally splined front and rear heads at opposite ends thereof in respective splined engagement with said wheel and said main shaft, an annularly shaped valve mounted in said casing for rotation about said main axis, said valve being in surrounding relation to said main shaft and said wobble shaft between the opposite ends thereof, said main shaft and said wobble shaft having aligned and transversely extending cross bores, a diametrically extending drive member attached to said valve and extending through said main and wobble shaft bores, said wobble shaft having a longitudinal bore extending from said cross bore thereof to and through said front head of said wobble shaft, and drive connection means including a keying shaft having a stem mounted in said wobble longitudinal bore which engages said drive member.
 2. A rotary piston machine according to claim 1 wherein the end of said stem is bifurcated and straddles said drive member, said keying shaft having a head portion at the end thereof opposite from said drive member, and a casing portion having abutting engagement with said keying shaft head portion.
 3. A rotary piston machine according to claim 1 wherein said drive member has a rectangular cross-section.
 4. A rotary piston machine according to claim 1 wherein said drive member has a circular cross section.
 5. A rotary piston machine according to claim 1 wherein said drive member has two parallel shaft portions.
 6. A rotary piston machine according to claim 5 wherein said parallel shaft portions have circular cross-sections. 